1. Field of the Invention
The present invention relates to a color conversion method, a color conversion program, and a recording medium.
2. Description of the Related Art
Recent years, in an image forming apparatus, when data is transmitted and received between different image processing devices, color conversion processing is often performed to secure color reproducibility. For example, in the transmission and reception of data between a scanner and a printer, a scanner response value (e.g., RGB values) is converted to a colorimetric value not depending on an image processing device, such as XYZ values or L*a*b* values, and then converted to an output value of the printer (e.g., CMYK value). Such a color conversion processing is performed, using a color conversion profile recording a correspondence relationship between the RGB values or the CMYK value depending on the image processing device, the XYZ values or the L*a*b* values not depending on the image processing device.
Generally, the color conversion profile is dedicatedly prepared for individual image processing device, for example as a color conversion profile for a scanner or a color conversion profile for a printer. Hereinafter, the color conversion profile for a scanner is referred to as a “scanner profile”, in the present specification. The scanner profile is a color conversion profile for holding, for example, a correspondence relationship between the RGB values and the XYZ values for a paper type of a document to be read by a scanner.
However, it is not realistic to previously prepare the scanner profiles for all types of paper used by a user, because the scanner profiles require a large-capacity storage device. Therefore, it can be considered that for example, a scanner profile is prepared only for a paper type frequently used, and an additional scanner profile of another paper type is created each time when needed. However, in order to create a scanner profile, it is necessary to output and measure color patches including combinations of C, M, Y, and K, and associate the RGB values with the XYZ values of the scanner. Therefore, there have been problems that the processing requires time, and an amount of paper used is increased.
In connection with the scanner profile, an image processing system is disclosed in JP 2008-278152 A. The image processing system is configured to search for a color conversion profile for a printer (hereinafter, referred to as “printing profile”) corresponding to a paper type closest to that of a document from printing profiles prepared for paper types. More specifically, the image processing system is configured to measure a paper white portion of the document by a spectrophotometer to search for a paper type closest to the paper type of the document from the paper types specified by a manufacturer, and select the printing profile corresponding to the paper type closest to the paper type of the document.
However, even if the spectrophotometer determines that the measured paper white portion has the same paper type, since glossiness or the like changes according to a difference between optical systems, the scanner response value may differ. Accordingly, even if the image processing system is configured to select a scanner profile corresponding to the paper type closest to the paper type of the document, based on a result of measurement of the paper white portion of the document by the spectrophotometer, the scanner profile may be inappropriately selected. Therefore, there is a possibility that the color reproducibility cannot be satisfactorily secured in color conversion processing.